This application is a competing renewal, designed to complete the designed follow-up on the Urinary Stone Prevention Trial, a randomized field trial of about 1000 recent adult male stone patients. The principal aim of this study is to determine if soft drink consumption (soda) is a contributing cause of stone recurrence. The 1-R01 design called for a follow-up of patients to three years or recurrence, with a one year accrual phase. Unfortunately, accrual proved to be more difficult than originally anticipated, with completion taking almost three years. The NlH has been appraised of this situation as soon as the applicants became aware of it. They requested us to economize as much as possible during the 1-R01 phase, and then apply for a two year competing continuation. This economization has been accomplished. with an anticipated balance of $15,000 left after completion of the 1-R01 phase. Interim analysis reveals that the original planning parameters are realistic, and that early termination of the study is not warranted.